[suggestion] Add Offline-SSID-Changer using gluon has_default_gw

[maurerle]

It would be very good to have an Offline-SSID-Changer package available here.
It should work with BATMAN_IV, BATMAN_V and babel

existing repos from single communities are:

• https://github.com/freifunk-kiel/gluon-ssid-notifier/
• ffh-check-connection: initial commit #9 (mesh protocol agnostic)
• https://github.com/eulenfunk/packages/tree/v2020.1.x/gluon-ssid-changer
• https://github.com/ffac/gluon-ssid-changer/
• https://github.com/Freifunk-Nord/gluon-ssid-changer
• https://gitlab.freifunk-stuttgart.de/firmware/gluon-ssid-changer
• https://github.com/tecff/gluon-packages/tree/main/tecff-ssid-changer (supports has_default_gw and owe)

A try to put something like this upstream failed, so I think it would be best to have this package here.

Recently gluon got a mesh-agnostic way to receive the online state and neighbours:

• gluon-online-status concept gluon#2228

So it would be cool to have a package which relies on this functionality.

[rotanid]

Recently gluon got a mesh-agnostic way to receive the online state and neighbours:

* [gluon-online-status concept gluon#2228](https://github.com/freifunk-gluon/gluon/issues/2228)

So it would be cool to have a package which relies on this functionality.

this does not replace much of the functionality in most of these ssid-changer solutions.
have a look at tecff/gluon-packages@0e5f16f and you can see how little this changes.